Optical-scanning system employing laser and laser safety control

ABSTRACT

An optical-scanning system including a laser, a multi-faceted, rotational scanning mirror, and system-monitoring laser safety structure operatively and informationally connected respectively to the laser and to the mirror and the drive motor for the mirror for altering the effective power output of the laser in response to current operational status of the system as determined by current operational status of the rotating mirror. The safety structure enforces on the laser a duty cycle of operation which is less than 100-percent, causes the laser to power down to a low &#34;sleep&#34; operating level at times other than during a normal scanning sweep, de-powers the laser entirely if either the drive motor for the mirror is not enabled or the rotational speed of the mirror is below full normal operating speed, and also positively de-powers the laser when a user shuts down the system.

TECHNICAL FIELD

This invention relates to an optical-scanning system, and moreparticularly, to such a system which employs a laser whose beam isscanned, and control circuitry which monitors system operation tomaximize laser safety vis-a-vis the eyes of a user of, or someone inproximity to, the system. While the system of the invention has, as willbe appreciated by those skilled in the art, relatively widespreadutility, an arena in which it has been found to offer particular,immediate utility is that of a graphic data-acquisition system fortracking and assessing the operational status, relatively to a writingsurface area, of a write-effective component, such as a pen and aneraser. Because of this situation, a preferred embodiment of theinvention is described herein in conjunction with such a graphic system.

BACKGROUND AND SUMMARY OF THE INVENTION

U.S. Pat. No. 5,248,856 for CODE-BASED, ELECTROMAGNETIC-FIELD-RESPONSIVEGRAPHIC DATA-ACQUISITION SYSTEM by Mallicoat, issued Sep. 28, 1993,describes a graphic data-acquisition system with respect to which thesystem of the present invention is an improvement, and is incorporatedin this disclosure for illustration purposes. Accordingly, the fulldisclosure of that patent is hereby incorporated by reference into thisdisclosure.

That patented data-acquisition system takes the form of a code-based,electromagnetic-field-responsive (and preferably optically responsive)system employing an active pair of transceivers, each including arotating, multi-faceted scanning mirror and a laser which is therebyscanned across a writing-surface area for the purpose of tracking theposition of, and noting certain characteristics respecting, differentwrite-effective components, such as those just mentioned above. While itis very unlikely that someone using, or located near, this kind of asystem would ever be in a position to have the beam from a laser in thesystem directly strike the eye, there is some remote possibility thatthis could occur. Given this even remote possibility, there is a needfor attention, addressed by the present invention, to assure that thesystem includes certain internal monitoring safety features that willminimize the likelihood of such an occurrence either occurring, or, ifoccurring, producing any appreciable damage. The system of the presentinvention, accordingly, and pursuant to a key object of the invention,addresses itself to several concerns relating to imagined situationswhere laser beam/eye interaction could occur, and focuses on providinginternal monitoring and control structures and substructures whichreduce, as much as possible, the likelihood of a catastrophiceye/laser-beam encounter.

In particular, when a graphic, data-acquisition system of this type isin normal operation, a laser beam typically is scanned in successivescanning sweeps through a scanning zone which is located near awriting-surface area, and there is some possibility that an objectimpinged in that zone by the laser beam could reflect outwardly towardthe eye of a nearby person. To deal with this possibility, the system ofthe present invention, inter alia, forces on such a beam what might bethought of as a controlled operating duty cycle, whereby the "effective"power of the beam, during normal operation, is reduced well below thenominal operating power level for the beam. Specifically, the system ofthe invention utilizes a blanking/un-blanking control "mechanism" andsignal, whereby the particular laser involved operates for only a shortperiod of time relative to each revolution of a multifaceted scanner.

Backing this up, and as a further safety measure, the system of theinvention incorporates substructure which monitors the blanked or"sleeping" period of time for the laser to assure that if, for somereason, the laser does not shut down to what is referred to herein as a"sleeping" power level, power flow is completely and immediately shutoff to the laser and to the scanner.

A further safety consideration taken into account in accordance with theinvention is that the laser is not permitted to be powered except undercircumstances when (1) the drive motor for the associated scanner isenabled and (2) the associated driven scanner is in fact operating atfull scanning speed, or rpm.

Finally, the safety features of the invention include controls wherebywhen a user of the system gives a command to shut down system operation,power is immediately cut off from the laser.

Thus, in addition to providing positive control over the effectiveoperating power of a scanned laser during normal operation, the systemof the present invention monitors other areas of "normal" activity, anddisables the laser when a related abnormality appears.

These and other objects and features which are offered and attained bythe invention will become more fully apparent as the description whichnow follows is read in conjunction with the accompanying drawings.

DESCRIPTIONS OF THE DRAWINGS

FIG. 1 is a front elevation, in schematic form, illustrating a graphicdata-acquisition system including the monitoring safety-feature systemof the present invention.

FIG. 2 is a block/schematic diagram of the system of the invention.

FIG. 3 is a fragmentary, and somewhat augmented, detail of the diagramof FIG. 2 illustrating certain safety-control features.

FIG. 4 which is generically like FIG. 3, illustrates certain othersafety-control features of the system of the invention.

DETAILED DESCRIPTION OF, AND BEST MODE FOR CARRYING OUT, THE INVENTION

Turning attention now to the drawings, and referring first of all toFIG. 1, indicated generally at 10 is a graphic data-acquisition systemincluding, as will be described, an optical-scanning system constructedwith safety features proposed in accordance with the present invention.Associated with this data-acquisition system, as illustrated in FIG. 1,is a writing-surface area 12a of an upright, dry-erase whiteboard 12which includes an implement-support ledge 12b on which rest two, mobile,write-effective components,including a pen 14 and an eraser 16. Each ofthese two components is constructed with encoded, retroreflectivestructure as described in the above-referenced '856 U.S. patent.

Located at two, spaced stations adjacent the upper corners of board 12are two, active transceiver structures 18, 20 which are alike inconstruction, and which are formed of components and circuitry that areof conventional and readily available commercial design. Each of thesetransceiver structures includes a laser, also referred to herein as alight-beam source, a five-facet (equilaterally pentagonal) power-rotatedscanning mirror, also referred to herein as a rotational scanninginstrumentality, appropriate optics associated with the laser, andcircuitry which, inter alia, monitors the onness and offness (powerlevel) of the laser, as well as the current rotational speed of thescanning mirror. Output signals relative to these two matters is madeavailable from this circuitry, and is used, as will be explained, in theimplementation of the present invention.

As is explained in the '856 patent, structure 18 functions to create,over and closely adjacent writing-surface area 12a, a pattern of scannedradiation in a scanning zone which is partially bounded by dash-dotlines 18a, 18b. Scanning occurs by structure 18 in successive sweeps ina counter-clockwise, rotary direction in FIG. 1. As the '856 patentpoints out, certain substructure within transceiver structure 18responds to any return-response radiation that returns from a designatedreflecting object within the scanning zone to effect a datastream whichis interpretable to track the position and to note the character of awrite-effective component disposed in proximity to writing-surface area12a. Structure 20 operates in a similar fashion to contribute to thescanning zone a pattern of clockwise-scanned light lying betweendash-dot lines 20a, 20b. The scanning rate associated with transceiverstructure 20 is the same as that associated with structure 18, andherein is 83 scans-per-second.

The tracking-interpretable datastreams from structures 18, 20 are fedvia data bus 38 to a processing unit 40 which includes a unit portion 42labeled herein "IMPLEMENT X, Y LOCATION" that operates in accordancewith the descriptive material provided in the '856 patent regarding aprocessor (40) shown in that patent.

Further incorporated with system 10 in accordance with improvementsthereto described not only in this specification, but also described inthree, pending, companion patent applications, identified hereinafter,are special reflector structures 44, 46, 48, 50, positioned as shownadjacent the margins of writing-surface area 12a, and within processingunit 40, processing unit portions 52, 54, 56, labeled, respectively,"IMPLEMENT Z LOCATION", "CALIBRATION", and "LASER SAFETY". Unit portion56 embodies the bulk of the system-monitoring laser safety featurescontributed by the present invention. The three companion patentapplications just mentioned are: "MARKING SYSTEM WITH PEN-UP/PEN-DOWNTRACKING", filed Nov. 5, 1993, by Scott E. Wilson, Samuel W. Mallicoatand Donald H. Zurstadt; "CALIBRATION OF GRAPHIC DATA-ACQUISITIONTRACKING SYSTEM", filed Nov. 5, 1993, by Donald H. Zurstadt, Samuel W.Mallicoat and Scott E. Wilson; and "GRAPHIC DATA-ACQUISITION SYSTEMUTILIZING LIGHT-SOURCE STRUCTURE WITH EXTRANEOUS-LIGHT FILTERING", filedNov. 5, 1993, by Timothy A. Jenness and Scott E. Wilson. The entiredisclosures of these two companion applications are hereby incorporatedherein by reference.

As explained in the patent application titled "CALIBRATION OF GRAPHICDATA-ACQUISITION TRACKING SYSTEM", structures 44, 46, 48, 50 function toaid in time calculations relative to the scan sweeps of the two laserbeams, and in addition, to promote accurate positioning of these scansweeps relative to the location of writing-surface area 12a. The patentapplication titled "MARKING SYSTEM WITH PEN-UP/PEN-DOWN TRACKING"relates to and describes unit portion 52 of processing unit 40. Thethird-mentioned, companion patent application focuses onextraneous-light filter substructure employed in transceiver structures18, 20.

Turning attention now to FIG. 2 in the drawings, here the organizationaldetails of laser safety features 56 are set forth in a block/schematicway, and are pictured in association with the relevant componentportions of, for example, transceiver structure 18, whose relevantcomponents are embraced by the three brackets which are shown in thisdrawing figure. Similar association, not shown, exists with transceiverstructure 20. Beginning first with these several relevant components ofstructure 18, included is (1) the laser represented in a blockidentified as "LASER MODULE", (2) the scanner, represented by a blockmarked "SCANNER", including the above-mentioned, five-facet, rotatingmirror and an associated rotational drive motor, and (3) a laseronness/offness observing diode (or the like) swept by the scanner andcontained within a block marked "FAULT DETECTOR".

Other blocks shown in FIG. 2 include a "LASER CONTROL AMPLIFIER", "MOTORDRIVE CONTROL LOGIC", "DSP PROGRAM CONTROLLER", and "CONTROL LOGIC".These blocks represent a well-understood mix of hardware and softwareelements, and can internally be constructed in a number of differentways well within the skills of those skilled in the relevant art.Accordingly, internal details of construction, which form no specificpart of the present invention, are not presented and discussed herein.

Through a line marked "POWER" the LASER CONTROL AMPLIFIER suppliesoperating power to the laser in the LASER MODULE, and via a line marked"FEEDBACK", and in accordance with appropriate adjustments made in theLASER CONTROL AMPLIFIER, the nominal operating power level for thelaser, which is the power level intended for operation during eachscanning sweep, is controlled.

Under the control of the CONTROL LOGIC block, the MOTOR DRIVE CONTROLLOGIC, via conductor structure labeled "MOTEN", both enables and powersthe drive motor for the SCANNER, and provides an informationaldrive-motor enable signal to the LASER CONTROL AMPLIFIER. The SCANNER,via conductor structure labeled "MOTLOK", informs the DSP PROGRAMCONTROLLER, as well as the LASER CONTROL AMPLIFIER, when the scanningmirror structure is actually operating at the desired, full rotationalspeed for operation in the system. Among other things, before the LASERCONTROL AMPLIFIER will supply power to the LASER MODULE, it must haveavailable to it both a drive-motor enable (MOTEN) signal from the MOTORDRIVE CONTROL LOGIC, and a MOTLOK signal from the SCANNER. Conductorstructures MOTEN and MOTLOK, along with respectively associatedcircuitry, function herein as rotational-speed-monitoring anddrive-power-enable substructure.

Considering now FIGS. 3 and 4 along with FIG. 2, and considering what isreferred to herein as duty-cycle substructure, information provided theDSP PROGRAM CONTROLLER via the MOTLOK conductor structure is assessed inrelation to a system CLOCK, shown in dash-dot lines in FIG. 3. This"related" information is provided to the CONTROL LOGIC block, via aconductor marked "CLOCK", in which logic block a dashed block marked"FACET TIMING COUNTER" works in accordance with one of the features ofthe present invention to enforce an operating duty cycle on the laservia a control conductor marked "LASER BLANKING" which feeds a signal tothe LASER CONTROL AMPLIFIER. In accordance with the preferred embodimentof the invention which is now being described, it is intended that thelaser in structure 18 be energized at the selected normal operatinglevel only once during the "passage" of one of the five rotating facetsduring each revolution of the scanning mirror, and specifically so thatthe beam only operates long enough to implement a scan, during "passage"of that one facet, essentially between previously mentioned lines 18a,18b shown in FIG. 1. During the remaining portion of each revolution ofthe scanning mirror, i.e., during the "passages" of the other, four,successive mirror facets, the CONTROL LOGIC block supplies a LASERBLANKING signal to the LASER CONTROL AMPLIFIER, which results in thisamplifier dropping the operating power level of the laser from thenormal operating level to a much lower level, which is referred toherein as a "sleep" level. This sleep level is chosen so that even if,for some reason, the laser beam were to strike a person's eye, and evenfor an extended time period, no appreciable eye damage would result.However, and as will further be explained, such an extended exposuretime is not possible because of other safety features which areimplemented in accordance with the invention.

During the "sleep" portion of each operating revolution of the rotatingscanning mirror, the FAULT DETECTOR operates to confirm that the laseris in fact operating at the selected "sleep" power level, and ifoperating power goes above this level, sends a control signal, via aline marked "FAULT", to a FAULT ASSESSOR contained within the CONTROLLOGIC block, which assessor, upon making a fault assessment, causes theCONTROL LOGIC block to send a LASER SHUTDOWN signal to MOTOR DRIVECONTROL LOGIC via a conductor marked "LASER SHUTDOWN". The FAULTDETECTOR is also referred to herein as sleep-level-observingsubstructure.

The POWER, FEEDBACK, MOTEN, MOTLOK and FAULT conductor structures extendbetween system 10 and unit 40 via cable structure shown at 60 in FIG. 1.

Given the system organization which has just been described, let us now"travel through" the important and significant safety features offeredin accordance with this invention. During normal scanning operation,each laser is powered only during the passage of one of the five mirrorfacets during each revolution of the associated rotating mirror. Thisform of enforced duty-cycle control thus lowers what might be thought ofas the "effective" power of a laser to a level which is below that ofthe nominal normal operating power of the laser. During the passages ofthe four other scanning facets, i.e., between intended, successivescanning sweeps, if the laser fails to power down to the sleep levelunder control of the LASER BLANKING signal from the CONTROL LOGIC block,the FAULT DETECTOR produces an appropriate FAULT signal which results ina LASER SHUTDOWN signal being transmitted to the MOTOR DRIVE CONTROLLOGIC block. When this happens, the MOTOR DRIVE CONTROL LOGIC blockremoves the MOTEN signal, thereby both shutting down the LASER CONTROLAMPLIFIER so that power is cut off from the laser, and stopping motordrive for the SCANNER. When this occurs, and when the SCANNER slowsbelow its assigned operational speed, and redundantly, the MOTLOK signalis removed, and thus the LASER CONTROL AMPLIFIER is further assuredlydisabled from powering the laser. Thus, if some failure were to occurwhich interrupted duty cycle control for the laser, the possibility thatthe laser beam could be scanned through the scanning zone, and thuspotentially be available to strike a person's eye during other than theproper passage of the selected scanning facet, it is substantiallyreduced to zero.

At any time, such as during start up of the system, when the rotaryspeed of the SCANNER is below the designated and chosen scanning speed,a MOTLOK signal is denied the LASER CONTROL AMPLIFIER, and the latter isunable to power the laser. This prevents a situation where a slowlyswept, and thus longer-lingering, laser beam, could impinge a person'seye.

Whenever the DSP PROGRAM CONTROLLER, via the line marked "LASERREQUEST", calls for energizing of the laser, as if assuming that theproper scanning facet is moving into position, the FACET TIMING COUNTERin the CONTROL LOGIC block, with information coming from the DSP PROGRAMCONTROLLER also, determines whether this request is being placed at anappropriate time, and if it is, allows removal of the LASER BLANKINGsignal, and if it is not, keeps the blanking signal in place to hold thelaser in its "sleep" condition.

Whenever a user shuts down the system, the DSP PROGRAM CONTROLLER, viasystem-on-following substructure contained within it, so informs theMOTOR DRIVE CONTROL LOGIC which then removes the MOTEN signal. Thisimmediately causes the LASER CONTROL AMPLIFIER to shut down the supplyof power to the laser, and further causes the SCANNER to stop operating.

Accordingly, the system of the invention offers significant safetyfeatures which substantially eliminate from concern the possibility thatsomeone near the system would experience eye damage. Variations andmodifications well within the skill of those skilled in the art may, ofcourse, be made without departing from the spirit of the invention.

We claim:
 1. A graphic data-acquisition system for tracking andassessing the operational status of a mobile write-effective componentrelative to a defined writing-surface area, said system comprisingalight-beam source in the form of a laser, a power-operated, rotationalscanning instrumentality positioned adjacent said source and operable,with rotation, to scan a beam from the source in successive scanningsweeps through a scanning zone spaced closely adjacent and generallyspanning the writing-surface area, and system-monitoring laser safetystructure operatively and informationally connected, respectively, tosaid source and to said instrumentality, operable, in response to thecurrently understood operational status of said instrumentality, toalter accordingly the effective power output of said source, saidstructure including duty-cycle substructure which is responsive toinformation regarding instrumentality angular position to create apower-flow duty cycle for said source which is less than 100-percent,whereby the source is powered at one selected operating level during thetime of a scanning sweep, and powered at another, lower, selected sleeplevel between successive scanning sweeps.
 2. The system of claim 1,wherein said structure further includes sleep-level-observing structureoperable, under circumstances with the source intended to be powered atsleep level, to stop the flow of power to the source on observing anoperating power level above sleep level.
 3. The system of claims 1 or 2,wherein said structure contains rotational-speed-monitoring anddrive-power-enable substructure which allows the supply of power to saidsource only under circumstances of both drive-power enablement for, andconfirmed attainment of selected, normal, rotational operating speed by,said instrumentality.
 4. The system of claims 1 or 2, wherein saidstructure includes system-on-following substructure operable, on acommand being given to remove drive power from said instrumentality, tostop the flow of power to said source.
 5. The system of claim 3, whereinsaid structure includes system-on-following substructure operable, on acommand being given to remove drive power from said instrumentality, tostop the flow of power to said source.